BGKnight will obviously know more but there are two factions currently open. There is the 1905 confederation, which is a decentralized left-wing confederation, and Pervomay, which is an isolated police run set of stations. If those two don't work, you could create a character or play as a group of stalkers. Maybe the Reich needs a special agent.

1990: Israel
Metal Gear: Iran
New Vegas: Salvador
Brazil: Proletarian Unification Party
1936: Empire of Japan
1971: China
Kaiserreich: CSA
You either die Fo'Dolo or see yourself live long enough to be the Patton.